How much RAM for a VM?

Let’s say I have a 2017 MacBook Air with 8GB of DDR3 RAM. I want to run a VM, probably Windows 10, on said MacBook.

How much RAM should I allocate to the host/guest?

Also, is running a VM really feasible under these conditions? I will only really be using one OS at a time. Should I just use something like Bootcamp?

Thanks in advance.

Parallels will give you advice on a range of acceptable RAM to allocate; their advice is usually good and is probably less than you would think. Probably it will be in the range of 1-2 Gb in your situation. More RAM allocated tends to be counterproductive because if you slow down the host OS then everything slows down.

What you lack in RAM tends to be compensated for by the SSD in the Mac Air. While it would have been ideal for them to start with 16Gb RAM as the base model, it will probably be workable in your situation as long as you are not running something performance extreme on Parallels such as X-Plane or major video editing.

That depends on what you will be running on Windows. That doesn’t change because it is a VM.

I’ve run Quicken in Win10 on an 8GB Mac using VirtualBox, as well as some Avaya administration tools. Neither of which demand much from Windows, but I still prefer to give Windows 4GB of ram, and make sure I have nothing running in macOS.

I recommend you start with 4GB for Windows, you can always adjust up or down depending on performance, but I would not try to run Win10 with less than 2GB.


Keep in mind that you can frequently purchase a entry level Windows computer for about the same price as a copy of Windows and Parallels or VMware. And in your situation, you should get better performance running a real PC via Microsoft Remote Desktop.

After running Windows/VMWare for several years we moved our Mac users to PCs via MRD.

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Thanks for the quick responses, guys! 2 follow up questions, because I’m a VM noob:

  1. How much SSD (out of 128GB) should I allocate? I think the Win10 minimum is 20GB but will I need more than that?
  2. If I allocate RAM to the VM, will that portion of the RAM return to macOS when the VM is not running?

Try it - you may be surprised. Parallels documentation endorses Win 10 with RAM allocation as low as 0.5 Gb. I have found results to often be less than intuitive - especially on a machine with an SSD to allow for swapping RAM.

https://kb.parallels.com/112091

Even on my Mac Pro with 192 Gb RAM, Parallells considers 0.5 Gb to be acceptable as a RAM allocation for my VM:

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And even though I allocated considerably more, it is only using 290 Mb - even with Dragon Dictate running on the VM:

Most of my experience was with spinning HDs and users that complained bitterly when things got slow.

4GB resulted in a lot fewer calls :smile:

Yes, very different with mechanical HDDs

Then again - I doubt Apple would ever have released an 8Gb RAM Mac Air with a spinning hard drive - the SDD is what makes it so fast and the performance is quite good

There is little harm to allocating more as long as you use the default Expanding disk option - the space will only be used if needed.

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It’s been a few years but I used to run Parallels and Windows XP on my 2011 MBP. Started with 8gb but found it was paging excessively. Upgraded to 16 and had no issues with it. I was primarily running Visual Studio. Can’t remember if I had switched to a SSD at that time yet.

I love Parallels, but I would never even try to run it on anything less than a 16 GB Mac again. That’s for my usage, though. The 8/8 split is still too little for both Mac and VM. Your usage may not be as taxing. Would you buy either a Mac or a Windows box with only 4GB of RAM in it? That’s essentially what you have when you share the RAM with the VM (using a 50/50 split, obviously). If so, then you’ll do fine with it. If not…

For an 8 GB system, I would recommend setting it up as Boot Camp first, so you can boot directly into Windows and use your full hardware capacity when you need some extra oomph!. Then you can tell Parallels to use that Boot Camp partition as your VM. You get the best of both worlds at the expense of partition space (this method does not dynamically resize the volume like a regular VM does). I’d even go so far as to say that if you don’t have the SSD space for that, I would recommend using an external TB (not USB) drive for the Windows partition.

What Parallels lists as the minimum range for VM RAM really has a huge performance impact. Also, if I want to do something graphics intensive, like 3d modeling or gaming, I boot directly into Windows via Boot Camp instead of using it as a VM. Even on a 64GB system! Graphics is almost always the bottleneck – maybe I shouldn’t use 4k or Coherence Mode.

It all depends on the use case.

If you have an SSD in the Mac and your usage of Parallels is to access a Windows-specific website without using Coherence and not on a 4K monitor, then performance is fine with 1Gb or less RAM on a VM.

3D modeling or gaming - well that’s a whole different story.

Thanks everyone for the replies! I tried it out.

RAM was fine, I gave the VM 3 out of 8 GB and it ran. A little bit slow on both host/guest, but it worked fine.

My bigger problem was storage space. At 128GB total, I maxed out the available storage. I think going forward, I’ll either run it off an external drive like @SteveH mentioned, or I’ll use RDP into my laptop PC (it has a cracked screen or I’d just use it instead).

Thanks everyone!

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The SSD is fairly easy to replace on your Air. Just did it on my 2015. Check out IFixit for instructions. I got a drive from OWC. Took about 15 minutes for the swap and an hour or so to clone it.

I’m assuming you’re installing this VM for a purpose of some sort. So the answer to this question depends on that purpose.

Occasional IE tabs to test websites? I would think that a gig or two would be more than adequate.

Trying to run an old version of Photoshop? Much more expensive, RAM-wise.

I’d try allocating less than you think you need, and see if it works. You can always adjust it later.

Agree with this 110%. Allow more than you think you’ll need, but not more than you could reasonably spare if Windows does the fandango on your hard drive and fills it all up.

Also…go through Windows and see what optional “features” you can disable, as long as you don’t need them.

Windows at least used to have a setting in Control Panel to optimize your settings for “best performance” or something like that, and that disables all of the window chrome, the translucency, etc. And disabling all of that stuff obviously uses less processor, less RAM, etc. So if that’s not strictly necessary for your purpose, do it.

Also look into shutting down background services you don’t need, etc. I don’t have specific advice in this department, but I know there used to be some software that would help you do this. Or Microsoft has MSConfig:

https://answers.microsoft.com/en-us/windows/forum/windows_10-update/msconfig-the-system-configuration-tool/273dea8e-4cbe-47e9-8489-f400e879ce17

which lets you tweak a ton of misc. stuff and make Windows a little more streamlined, at the potential expense of features.

Regarding the disk space, I really like my Samsung T5. Can run VMs off of it without any significant performance degradation - although that’s on a 2018 Mac Mini with a 6-core i7 and 32 GB RAM, so your mileage may vary a touch - but the disk doesn’t seem to be the limiting issue. And they’re pretty reasonably-priced typically. :slight_smile:

Best of luck!

OMG I never thought of this! Will look into it.

The way I did the change of the SSD was to clone the old drive to an external SSD. Then boot from the external to verify it is working properly. I then swapped the internal SSD. Started back up, booting off the external. Formatted the new drive and cloned the external to the new internal. Shut down, remove external SSD, and boot off internal and verify that all is good. I went with a 1tb SSD so I wouldn’t have to worry about space for awhile.

Although to be honest, I’d probably buy a drive and tape it to the back of my MBA. Not the type that wants to crack the device open, even if I had the instructions and everything XD.